Forest management effects on vegetation regeneration after a high severity wildfire: A case study in the southern Cascade range

Abstract

Wildfires play a vital role in ecosystems and are one of the most significant natural processes that shape the northern Sierra Nevada and southern Cascade Mountain Ranges in northeastern California. At the same time, across the American West, a history of fire exclusion, timber salvage and harvest, and human-assisted reforestation has caused widespread changes in forest vegetation patterns over the past century. Federal agencies such as the National Park Service (NPS) and US Forest Service (USFS) have different missions and approaches to these land management activities, creating a mosaic of ecological conditions across managed landscapes both before and after wildfires. We studied vegetation recovery following a major fire that crossed jurisdictional boundaries to explore how management history (fire exclusion and timber harvest and salvage) and post-fire reforestation efforts may influence vegetation regeneration. Using both field-based data collection and remote sensing Normalized Difference Vegetation Index (NDVI) analyses, we assessed differences in vegetation communities found in the NPS and USFS portions of the footprint of the 2012 Reading Fire in northeastern California. We found that a legacy of timber harvest combined with fire exclusion was associated with denser shrub regeneration and minimal sapling recovery. In this context, areas that were reforested post-fire returned a relatively diverse and abundant suite of mixed-conifer tree species to the landscape. In areas with a history of fire exclusion that regenerated without human interference after the fire, saplings did establish on their own but were predominantly white fir (Abies concolor), a shade-tolerant species that is known to increase wildfire severity.